1. Field of the Invention
This invention relates generally to the creation, distribution and display of electronic documents and more particularly to the viewing of electronic documents.
2. Description of the Related Art
In this "information era", it has become increasingly common to create, transmit, and display documents in electronic form. Electronic documents have a number of advantages over paper documents including their ease of transmission, their compact storage, and their ability to be edited and/or electronically manipulated.
An electronic document typically has information content (such as text, graphics, and pictures) and formatting information which directs how the content is to be displayed. With recent advances in multimedia technology, documents can now also include sound, full motion video, and other multimedia content.
An electronic document is provided by an author, distributor or publisher (hereafter "publisher") who often desires that the document be viewed with the appearance with which it was created. This, however, creates a problem in that electronic documents are typically widely distributed and, therefore, can be viewed on a great variety of hardware and software platforms. For example, the video monitors being used to view the document can vary in size, resolution, etc. Furthermore, the various software platforms such as DOS, Microsoft Windows.TM., and Macintosh.TM. all have their own display idiosyncrasies. Also, each user or "reader" of the electronic document will have his or her own personal viewing preferences, which should be accommodated, if possible.
A solution proposed for this problem is to provide the content information of an electronic document without a predetermined final format. The content information then can be dynamically formatted (including the creation of line breaks, page breaks, etc.) as it is read by the user. Examples of this solution include the Standard Generalized Mark-Up Language (SGML) and the Office Document Architecture (ODA), both of which emerged through government/military standardization efforts.
The aforementioned proposal has never gained wide-spread acceptance. One reason is that formatting complex documents "on the fly" can be slow and can, in practice, produce results that may be aesthetically unpleasant. Another is that when publishers distribute documents, they intend that the documents have a particular appearance for its readers. Solutions which involve dynamic document formatting suffer from the undesired result that the publisher can't control the final appearance of the document. This may be adequate for some content information (such as technical proposals or informal memos), but for the bulk of business and artistic communication, presentation may be a critical factor.
A partial solution to this problem is to provide a document in a predetermined format where the appearance of the document as viewed by a reader is as it was intended by the publisher. One such predetermined format is the Portable Document Format.TM.(PDF.TM.) developed by Adobe Systems, Inc. of Mountain View, California. An example of software for creating and reading PDF documents is the Acrobat.TM. software, also of Adobe Systems, Inc. The Adobe Acrobat software is based on Adobe's PostScript.RTM. technology which describes formatted pages of a document in a device-independent fashion. However, PostScript technology is not well suited to the aforementioned dynamic reformatting process.
Electronic documents often include one or more articles. For example, a newsletter may include a main article and several secondary articles. Not infrequently, the articles are broken into various sections which may be scattered throughout the document. For example, a main article might start on page one of a newsletter, and conclude on pages three and four of the newsletter. It is therefore apparent that documents transmitted in a predetermined format (such as PDF) may include article sections that are physically separated within the document. This can make the reading of a particular article difficult. While prior software, such as the aforementioned Adobe Acrobat.TM. software, may include a rich set of pan and zoom options, it can still be difficult to read an article in content flow order to follow the "thread" of the article. Other software, including publishing software such as Personal Press.TM. of Adobe Systems, Inc. permits columns of an article to be "chained" together, but does not aid a reader in reading the article.